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Not Applicable.
1. Field of Technology
The present invention relates generally to transport belts and webs.
2. Description of Related Art
Conveyor belts, such as endless belts, are known in the art, useful for continuously transporting materials from one point to another. Note that by xe2x80x9cendless,xe2x80x9d a continuous loop is denoted; in actuality, the belt can be a flat strip of material in which the two ends are joined or seamed. An endless belt spans and has a partial wrap around two or more rollers to form a loop, where at least one of the rollers is driven to drive the belt around the transport loop. Frictional or vacuum forces, or both, are generally used to adhere materials to be transported to an outer surface of the belt. One problem associated with endless belt transports is keeping the belt properly aligned on the set of rollers.
An endless belt cycled over rollers generally needs to be steered. Lateral movement of a belt with respect to an axle of a rollerxe2x80x94also referred to in the art as xe2x80x9cdrift, xe2x80x9cwalkxe2x80x9d and other colloquial termsxe2x80x94needs to be restrained; otherwise, the belt is found to move partially or completely off the rollers during repeated cycling. The challenge of keeping the belt properly aligned is magnified when the material being transported must be transported to a very specific location. For example, in a hard copy apparatus, transporting a sheet of print media, e.g., paper, to a specific printing zone where images or alphanumeric text are formed affects print accuracy and quality. Some of the belt tracking and steering systems attempting to keep the belt running straight include those referred to as xe2x80x9cactive steeringxe2x80x9d and xe2x80x9cpassive steering.xe2x80x9d
Passive steering may be accomplished with a mechanism that biases the belt to a known and fixed position. For example, the belt may be steered by a flange on at least one of the rollers or by one or more stationary guides along at least one lateral edge of the belt. Passive steering generally leads to the eventual failure of the belt by wearing and cracking the belt. Furthermore, passive tracking methods force the belt into one drive line, which can lead to increasing torque loads on drive motors. Non-metallic and otherwise more flexible belts can also be passively steered by xe2x80x9ccrowningxe2x80x9d one or more of the rollers, an option generally not available for metal and less flexible belts without yielding the belt materially. Moreover, passive steering mechanisms can be thrown off by changes in friction which can be caused by different tensile loads on the belt, higher or lower vacuum levels, heat, wear, normal forces, and the like.
Active steering is the use of a sensing device that feeds real time position information back to a steering roller of the belt transport loop mechanism. A change in the mechanism is initiated to produce a steering effect on the belt to correct for any deviation from its desired position. One active steering solution is to adjust the belt tension on one side. Another active steering solution is to sense current belt position and to steer the belt accordingly by a predetermined movement of the steering roller. Active belt tracking and steering systems typically include: a sensor for determining when the belt is deviating from a desired alignment, a steering roller which can be skewed relative to the line of travel of the belt within a field of view of the sensor, and a steering roller control associated with the sensor and roller for controlling the axial position of the steering roller. Electronic circuits, programmed routines, and other equivalents known to those skilled in the art, may be used to monitor signals from the sensor, determine required adjustments, and then make adjustments using the re-positioning control.
Note that the same problem and similar solutions are also associated with general conveyor belt systems and web control.
A steering device and method for a steering roller guiding a flexible band is described. The device includes a worm and worm wheel transmission mounted to the roller at one axial end thereof. Coupled to the transmission, a motor is provided for receiving signals for bidirectionally steering the band on the roller via the transmission.
The foregoing summary is not intended to be an inclusive list of all the aspects, objects, advantages and features, nor should any limitation on the scope of the invention be implied therefrom. This Summary is provided in accordance with the mandate of 37 C.F.R. 1.73 and M.P.E.P. 608.01(d) merely to apprise the public, and more especially those interested in the particular art to which the invention relates, of its nature in order to be of assistance in aiding ready understanding of the patent in future searches.